An image drawing apparatus that draws a 3D image, and the like generates graphic information on a 2D display surface based on, for example, vertex information of a figure (for example, see Japanese Patent Application Laid-Open Nos. H11-31236, H10-222695, H9-180000, and 2000-30081). Further, the drawing apparatus generates an image displayed on the 2D display surface based on the generated graphic information. For example, the image drawing apparatus includes a frame buffer storing a color of a pixel and a depth buffer storing a depth (Z value) of the pixel.
In a general image drawing apparatus, the frame buffer and the depth buffer need a memory size as many as the number of pixels on the display surface. For example, when the display surface is 800×600 pixels and a data size (a total value of the color and the depth) per one pixel is 8 bytes, the frame buffer and the depth buffer need a memory size of approximately a total of 3.7 MB.
In order to store data as many as the number of pixels on the display surface, the buffers (the frame buffer and the depth buffer) having a large memory size are needed. For example, when the frame buffer having the large memory size, and the like are formed as an SRAM in the drawing apparatus, a circuit dimension and cost are significantly increased. Further, when the frame buffer having the large memory size, and the like are formed as a DRAM outside the drawing apparatus, there is a problem in that power consumption by inputting and outputting data in the external DRAM is increased and cost by mounting the DRAM as another chip is increased.